For Legend of the Five rings, and sometimes for 7th Sea, using roll and keep, you get to reroll 9s, and sometimes even 8s. Often you can only reroll them once per die.

It would be nice if the dice roller would allow you to specify the values that it will reroll (ie reroll top 3 values). It would also be handy if you could set several reroll values, and specify how many each of them can happen per die.

With both of these mechanics in place, I could then roll something like 10k4+25, rerolling 8s once, and rerolling 9s and 10sw as often as they occur.

I know it sounds kind of corner case, but I have a character in a game now that will be making that roll a lot; every time he uses a particular skill he'll be rolling that, or something similar, up to 9 times per attempt (he gets 9 rerolls). And that skill is used to activate most of his capabilities. This character is, admittedly, probably at the extreme of this sort of situation, but there are many abilities that do cause similar situations (sans the rerolling like crazy part).